2013 Ties for 4th Hottest Year on Record

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It's official: 2013 was one of the hottest years on record for
the planet, tying 2003 as the world's fourth warmest year since
record keeping began in 1880, a new analysis shows.

In 2013, the combined global land and ocean surface temperature
was 1.12 degrees Fahrenheit (0.62 degrees Celsius) above the 20th
century average of 57 F (13.9 C), according to the annual climate
report released by the U.S. National Oceanic and Atmospheric
Administration (NOAA).

In a separate analysis, scientists at NASA came up with slightly
different results, finding that the global temperature from 2013
tied with 2009 and 2006 for the seventh warmest year on record.
The two agencies use "slightly different methods, but overall,
their trends show close agreement," a statement from NASA noted.
[ Video:
Watch 60 Years of Rising Temperatures ]

Climate data from the past 134 years reveal a
long-term trend of
global warming. Climate scientists attribute the bulk of this
warming to the buildup of greenhouse gases, such as carbon
dioxide, in the atmosphere due to emissions from industry, power
and transportation. The level of carbon dioxide in Earth's
atmosphere, which hit 400 parts per million in 2013, is
now higher than at any time in the last 800,000 years, according
to NASA. (Parts per million denotes the volume of a gas in the
air; in this case, of every one million air molecules, 400 are
carbon dioxide.)

Temperatures around the world have climbed an average of 0.11
degrees Fahrenheit (0.06 degrees Celsius) each decade since 1880,
but they've risen even more significantly since the 1970s — at a
rate of 0.28 degrees Fahrenheit (0.16 degrees Celsius) per
decade, according to NOAA. Last year marked the 37th year in a
row that the global average temperature was higher than the 20th
century average, and the 15 hottest years on record include all
13 thus far in the 21st century (2000-2013).

Not every region experienced above-average
warmth in 2013. The Netherlands, for example, saw its
coolest spring in more than four decades, and Russia recorded its
coldest March in the past 50 years, with temperatures plummeting
as much as 18 degrees F (10 degrees C) below average in some
areas. Nonetheless, no part of the world recorded its coolest
annual temperature last year, according to NOAA.

NASA scientists emphasized that short-term weather patterns will
always cause fluctuations in average temperatures from one year
to the next. In other words, the long-term trend of global
warming doesn't mean each new year will be warmer than the last.
But climate scientists now anticipate each successive decade will
be warmer than the last because of the high level of greenhouse
gases in the atmosphere, according to NASA.